(1) Field of the Invention
The present invention relates to an underwater agitation pump which can suck soil, sand or the like which contains block-like material or string-like material in a dredging site, civil engineering work site, a sewage treatment plant, a sedimentation pool or a pit within a plant, an inside of a manhole or the like while efficiently agitating such soil, sand or the like and can discharge such sand, soil or the like to a given place.
(2) Description of the Related Art
Conventionally, as an underwater agitation pump which is served for the above-mentioned usage, there has been known an underwater agitation pump 100 which has a constitution shown in FIG. 19, for example.
As shown in the drawing, in this underwater agitation pump 100, an impeller casing 101 having a hollow disc-like shape is provided with a center suction opening portion 102 at a center portion of a lower surface thereof and a discharge opening portion 104 which is connected to a discharge pipe 103 at a peripheral portion thereof. In the inside of the impeller casing 101, a disc-like impeller 105 is rotatably disposed. The impeller 105 is provided with a center suction opening portion 106 at a center portion of a lower surface thereof and forms a plurality of radial flow passages 107 in the inside thereof in a circumferentially spaced-apart manner. Further, the impeller 105 is fitted on and is connected to an output shaft 109 of a water-tight motor 108 which is mounted on an upper surface of the impeller casing 101.
Further, a cylindrical strainer 111 having a bottom wall 110 is contiguously mounted on a lower portion of the impeller casing 101 and an annular support frame 112 is mounted on a lower surface of the cylindrical strainer 111.
Still further, the output shaft 109 of the water-tight motor 108 to which the impeller 105 is fixedly secured is extended downwardly after passing through the center suction opening portion 106 of the impeller 105, the center suction opening portion 102 of the impeller casing 101 and the cylindrical strainer 111 and forms an agitator mounting shaft 113. An agitator (cutter fan) 114 which protrudes a plurality of blade members in the radial direction from an outer peripheral surface of a body thereof is fixedly secured to a distal end of the agitator mounting shaft 113.
Due to such a constitution, when the watertight motor 108 is driven, the impeller 105 and the agitator 114 are integrally rotated so that a negative pressure is generated in the inside of the impeller casing 101 and soil, sand or the like which is piled up below the underwater agitation pump 100 is agitated by the agitator 114. Accordingly, the agitated soil, sand or the like is sucked into the impeller casing 101 through the cylindrical strainer 111 and thereafter is discharged to a desired place through the discharge opening portion 104 and the discharge pipe 103.
However, the above-mentioned underwater agitation pump 100 still has a following task to be solved. That is, as shown in FIG. 19, the agitator mounting shaft 113 which mounts the agitator 114 on the distal end thereof passes through the center suction opening portion 106 of the impeller 105 and the center suction opening portion 102 of the impeller casing 101. Accordingly, as shown in FIG. 20, a soil/sand inflow effective area A2 is formed of a narrow annular area which is defined between an inner peripheral surface of the center suction opening portion 106 or the center suction opening portion 102 and an outer peripheral surface of the agitator mounting shaft 113.
Accordingly, when block-like material or string-like material is mixed in the soil, sand or the like, such string-like material or flexible cloths such as vinyl cloths or the like are entangled in the agitator 114, the agitator mounting shaft 113, the cylindrical strainer 111 or the like and the block-like material and the string-like material clog the soil/sand inflow effective area A2. As a result, the operation of the underwater agitation pump becomes difficult or impossible so that there is a possibility that the soil/sand suction operation becomes difficult or impossible.
The present invention has been made to solve such a drawback and it is an object of the present invention to provide an underwater agitation pump which can reliably and efficiently suck and discharge soil, sand or the like even when the sand, soil or the like includes block-like material or string-like material.
To achieve the above-mentioned object, according to a first aspect of the present invention, there is provided an underwater agitation pump which comprises an impeller casing in which an impeller driven by a motor is rotatably accommodated, an agitated material suction guide cylinder being constituted of a hollow cylinder which has one-end opening portion thereof integrally connected to a center suction opening portion of the impeller while passing through a center opening of the impeller casing and having the other-end opening portion thereof extended downwardly, the agitated material suction guide cylinder further forming an agitated material suction passage in the inside thereof, and an agitator which is mounted on an outer periphery of the other-end opening portion of the agitated material suction guide cylinder.
In the above-mentioned constitution, a proximal end of the agitated material suction guide cylinder which is formed of the hollow cylinder is directly communicably connected with the center suction opening portion of the impeller and the agitator is mounted on the outer peripheral portion of the distal end of the agitated material suction guide cylinder. Accordingly, it becomes possible to make an inner diameter of the agitated material suction guide cylinder substantially equal to an inner diameter of the center suction opening portion of the impeller and an agitator mounting shaft which has been necessary in a conventional underwater agitation pump is made unnecessary, whereby the agitated material suction passage formed in the inside of the agitated material suction guide cylinder can ensure a sufficiently wide agitated material inflow area. Accordingly, it becomes possible to sufficiently agitate soil, sand or the like in which block-like material or string-like material is mixed with use of the agitator and, at the same time, it is possible to smoothly suck such soil, sand or the like in which the block-like material or the string-like material is mixed into the impeller casing through the agitated material suction guide cylinder.
Further, since it becomes possible to make an outer diameter of the agitated material suction guide cylinder substantially equal to the inner diameter of the center suction opening portion of the impeller, compared to the agitator mounting shaft of the conventional underwater agitation pump which mounts an agitator on a distal end thereof, the outer diameter of the agitated material suction guide cylinder can be remarkably increased so that the winding or the wrapping of the string-like material around the agitated material suction guide cylinder can be reliably prevented. Further, compared to the agitator mounting shaft of the conventional underwater agitation pump, the outer diameter of the agitated material suction guide cylinder can be remarkably increased and hence, the section modulus can be remarkably increased so that the mechanical strength of the agitated material suction guide cylinder can be increased whereby it becomes possible to increase the agitator supporting strength and to prevent the rapture or the like of the agitated material suction guide cylinder reliably.
Still further, since the other-end opening portion of the agitated material suction guide cylinder which forms an suction opening of the agitated material is formed at a position which is downwardly protruded from the center suction opening portion of the impeller, such a suction opening can be located close to a waterbed compared to an agitated material suction opening of the conventional underwater agitation pump. Accordingly, it becomes possible to simultaneously perform the agitation and the suction of sediment (agitated material). In this manner, while ensuring the sufficiently wide agitated material inflow area in the inside of the agitated material suction guide cylinder, the suction efficiency of the sediment (agitated material) can be further enhanced.
Although the agitated material suction guide cylinder can be formed with the impeller by an integral molding, the agitated material suction guide cylinder can be formed as a body separate from the impeller and can be connected to the impeller by means of bolts. Further, the agitated material suction guide cylinder is formed as a body separate from the impeller, a female threaded portion is formed in the center suction opening portion of the impeller, a male threaded portion is formed in the one-end opening portion of the agitated material suction guide cylinder, and the agitated material suction guide cylinder is connected to the impeller by engaging the male threaded portion with the female threaded portion. In this manner, when the agitated material suction guide cylinder is constituted of a member separate from the impeller, the constitutions of the impeller and the agitated material suction guide cylinder can be simplified so that they can be manufactured at a low cost.
The agitated material suction guide cylinder may be comprised of a large-diameter body portion and a stepped distal-end narrowed-diameter portion which constitutes the other-end opening portion, and the agitator is formed by mounting a plurality of triangular agitator constituting members which are extended in the radial direction in a circumferentially spaced apart manner on a stepped portion of the stepped distal-end narrowed-diameter portion. In this case, the agitator constituting members plays a role of guides for the string-like material so that the entanglement of the string-like material in the agitator can be further reliably prevented.
Although the agitator may be mounted on the outer peripheral portion of the other-end opening portion of the agitated material suction guide cylinder by welding or the like, the agitator may be integrally formed with the agitated material suction guide cylinder by molding the other-end opening portion of the agitated material suction guide cylinder in a non-circular shape (triangular shape, quadrangular shape, polygonal shape, star-like shape or the like). In this case, since the agitator can be integrally formed with the agitated material suction guide cylinder, the agitator supporting strength can be increased. Further, since the agitated material suction guide cylinder and the agitator can be integrally formed, manufacturing steps can be decreased in number so that they can be manufactured at a low cost.
A helical feeding blade may be mounted on an inner surface of the agitated material suction guide cylinder. In this case, along with the rotation of the agitated material suction guide cylinder, the helical feeding blade is integrally rotated so as to generate a lifting force so that the suction efficiency of the underwater agitation pump can be enhanced. Accordingly, even when the agitated material may be made of material having a high-concentration (soil, sand, muddy water or the like of low fluidity having a small water content), the agitated material can be efficiently and reliably sucked.
A sub water supply pipe which has an upper inlet opening thereof opened in water may have a lower outlet opening thereof disposed in the vicinity of the agitator and directed toward the agitator. In this case, even when the concentration of the soil, sand or the like is excessively high, the soil, sand or the like can be diluted with the sub water so that the soil, sand or the like can be made to smoothly flow into the inside of the agitated material suction guide cylinder.
A peripheral wall for preventing collapsing and inflow of soil, sand or the like which concentrically surrounds the agitated material suction guide cylinder and has a lower end thereof opened may be contiguously connected to a lower portion of the impeller casing, a water reservoir space may be formed between the agitated material suction guide cylinder and the peripheral wall for preventing collapsing and inflow of soil, sand or the like, and a lower outlet opening of a sub water supply pipe which has an upper inlet opening thereof opened in water may be communicably connected to the water reservoir space. In this case, due to the presence of the peripheral wall for preventing collapsing and inflow of soil, sand or the like, it becomes possible to prevent soil, sand or the like from being collapsed and clogging the other-end opening portion of the agitated material suction guide cylinder which forms a suction opening of the agitated material. Further, due to the presence of the water reservoir space, the soil, sand or the like having a high-concentration can be agitated while being diluted with the sub water and thereafter can be made to smoothly flow into the inside of the agitated material suction guide cylinder.
Further, to achieve the above-mentioned object, according to a second aspect of the present invention, there is provided an underwater agitation pump which comprises an impeller casing in which an impeller driven by a motor is rotatably accommodated, an agitated material suction guide cylinder being constituted of a hollow cylinder which has one-end opening portion thereof integrally connected to a center suction opening portion of the impeller while passing through a center opening of the impeller casing and having the other-end opening portion thereof extended downwardly, the agitated material suction guide cylinder further forming an agitated material suction passage in the inside thereof, a strip-like agitator mounting member which spans the other-end opening portion of the agitated material suction guide cylinder, and an agitator which is fixedly secured to a center portion of the agitator mounting member, wherein portions which constitute the other-end opening portion of the agitated material suction guide cylinder and are disposed at both sides of the agitator mounting member are notched toward the impeller to form a pair of agitated material suction openings.
Also according to this aspect of the present invention, the agitation of soil, sand or the like by the agitator and the suction of the soil, sand or the like by the impeller can be simultaneously performed so that the suction and discharge efficiency can be enhanced. Further, since a pair of agitated material suction openings are formed at both sides of the agitator mounting member, the soil, sand or the like which contains the string-like material or the block-like material can be smoothly sucked into the impeller casing through the agitated material suction openings and thereafter can be discharged from the impeller casing.